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Field Notes — Location Status Report

Field Notes: Borneo

One of the world's oldest rainforests, split between Indonesia, Malaysia, and Brunei, and home to orangutans, pygmy elephants, and one of the world's most threatened rhino populations. Here's what the evidence shows about its current state.

Critically Endangered Bornean orangutan (IUCN)
~1,500 Bornean pygmy elephants remaining
Functionally extinct Bornean rhinoceros, in the wild
Published July 2026 Last reviewed July 2026 Evidence level Strong Reading time 7 min

Status & Geography

Borneo is the third-largest island in the world, its roughly 743,000 km² divided between Indonesia (Kalimantan), Malaysia (Sabah and Sarawak), and Brunei. Its rainforests are estimated to be among the oldest continuously existing forest ecosystems on Earth, and the island is considered one of the most biodiverse places on the planet, hosting an estimated 15,000 plant species and over 220 mammal species, many found nowhere else.

Established fact

Annual forest loss in Borneo has been estimated at around 1.54% per year in recent projections, with the island's forest cover projected to decline by a further 19% by 2032 if current trends continue. Between 2000 and 2010 alone, Borneo lost an average of roughly 3,234 km² of forest per year.

Source: Deforestation projections for Bornean orangutan range, Perspectives in Ecology and Conservation, 2022

Ecosystem

Borneo's lowland dipterocarp rainforest is one of the most structurally complex forest types on Earth, with a closed canopy that can exceed 60 meters and support several distinct vertical habitat layers. Much of this lowland forest — the type most accessible for logging and agricultural conversion — has already been cleared or degraded, pushing surviving wildlife populations increasingly into upland and protected-area remnants that are harder to access and generally less suitable for large-bodied species like elephants and orangutans.

Key Species

Bornean Orangutan (Pongo pygmaeus) Population has declined by roughly 100,000 individuals between 1999 and 2015 alone, driven primarily by palm oil and timber-related deforestation. Current range-wide estimates put the remaining population in the low hundreds of thousands, with continued declines projected through the 2030s under current land-use trends. Full species profile →
Bornean Pygmy Elephant (Elephas maximus borneensis) Around 1,500 individuals remain in the wild, confined mostly to the northeastern part of the island. Listed as Endangered on the IUCN Red List, with population decline of at least 50% estimated over the last three generations (roughly 60–75 years), driven by habitat fragmentation and conflict with plantation agriculture.
Bornean Rhinoceros (Dicerorhinus sumatrensis harrissoni) Declared extinct in the wild in Malaysia in 2015, with the country's last captive individual dying in 2019. A small number of individuals may persist in remote parts of Indonesian Kalimantan, but the subspecies is considered functionally extinct in the wild across almost all of its former Bornean range.

Threats

Palm oil and timber deforestationConversion of lowland rainforest to oil palm plantations and industrial logging concessions remains the best-documented driver of habitat loss across the island, with satellite-monitored clearing directly overlapping orangutan and elephant range.
Human-wildlife conflictAs forest is replaced by plantations, elephants and orangutans increasingly move through or feed in agricultural land, leading to retaliatory killing, poisoning, and capture that is difficult to fully document but widely reported by researchers and conservation groups operating on the ground.
Habitat fragmentationRoads, mining concessions, and plantation boundaries increasingly divide remaining forest into isolated patches too small to support viable long-term populations of large-bodied species, compounding the effect of outright forest loss.

Trend

1950Baseline point from which the Bornean orangutan population is estimated to have declined by more than half.
1999–2015Bornean orangutan population falls by an estimated 100,000 individuals, according to range-wide modeled estimates.
2015–2019Bornean rhinoceros declared extinct in the wild in Malaysia; last captive individual in the country dies in 2019.
2024Bornean elephant formally listed as Endangered on the IUCN Red List, reflecting a documented decline of at least 50% over three generations.
PresentForest loss continues at an estimated 1.54% per year, with further declines projected through the early 2030s absent stronger enforcement.

Conservation Measures

Protected-area networks, Roundtable on Sustainable Palm Oil (RSPO) certification, and cross-border cooperation between Indonesia, Malaysia, and Brunei under the "Heart of Borneo" initiative are the primary tools currently in use. Wildlife corridors connecting fragmented forest patches, and rescue-and-release programs for orangutans displaced by land clearing, are also active on the ground, though their long-term effectiveness at reversing — rather than just slowing — habitat loss remains debated.

Uncertainty & Evidence Gaps

Population figures for wide-ranging forest species like orangutans and elephants rely on indirect survey methods — nest counts and dung-density surveys extrapolated across large forest areas — which carry meaningful statistical uncertainty. The status of the Bornean rhinoceros in remote parts of Indonesian Kalimantan is particularly unclear, since no confirmed sighting has been independently verified in several years, meaning the subspecies could be functionally extinct across its entire range or could persist in very small, undetected numbers.